Injection volume, overload, and peak distortion

Speaking only to injection volume as I have actually seen it, rather than as it is usually described: the effect is real, it is smaller than the thread suggests, and the variance between people is larger than the effect.

This follows post #14 rather than contradicting it.

Column chemistry and particle size: smaller particles (1.7 μm) give better resolution and higher efficiency than larger particles (3.5 μm or 5 μm), at the cost of higher back pressure. Newer methods increasingly use smaller particles.

Source for the injection volume figure, since it was asked for. It is in the discussion rather than the abstract, which is why the version circulating is stronger than the paper is.

Reading the surrounding paragraph is worth the two minutes. The authors are more careful than their summarisers.

A request rather than an answer: could whoever has the primary source for injection volume post it? I have seen the claim three times this month and each version had lost a qualifier.

Where I part company with post #17, and it is a narrow parting.

Trifluoroacetic acid at 0.1 per cent is the near-universal ion-pairing additive for this work, and it also raises the baseline at 214 nanometres. That is why the same sample looks noisier at low wavelength.

Post #17 is the version of this I will quote in future. One addition.

The confident answers on injection volume and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.

Understood, and I withdraw the assumption I opened with.

Post #20 describes the usual case. This is about the unusual one.

I would be cautious about generalising from the injection volume example above. It is a good example. It is one example.

Confirming post #22 from a second method, which matters more than confirming it from a second person.

A chromatogram image at a resolution where you can see peak shape but not baseline detail is worth having and is not the same as the data. Ask for the integration table if the number matters.

Change the wavelength and the proportions change even though the sample has not. That is the reason the wavelength has to be on the document for the number to mean anything.

The arithmetic in post #22 is right; the assumption feeding it is the part to check.

An observation about injection volume that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.

Answering the question post #24 raises rather than the one it answers.

Injection volume: I would want to see the raw numbers rather than the summary before agreeing. Summaries lose exactly the information that would settle this.

Gradient delay volume differs between instruments and shifts the whole chromatogram. It is why a transferred method rarely reproduces retention times exactly on a different system.

Typical suitability criteria are a replicate area relative standard deviation below about two per cent, a tailing factor inside a defined window, a resolution minimum against a specified peak, and a plate-count floor.

The evidence for this is thinner than the way I have phrased it suggests.

A chromatogram image at a resolution where you can see peak shape but not baseline detail is worth having and is not the same as the data. Ask for the integration table if the number matters.

I had read the opposite somewhere and cannot now find where, which tells me something.